Brightwisp

Wisps are widely believed to be the spiritual remnants of long-deceased souls. They display only limited cognitive abilities and react to their surroundings driven more by primitive inherent tendencies than complex reasoning.
Using these observations as a foundation for their theory, certain scholars have formed the hypothesis that when wisps and plasmoids cross over into Eorzea from the void, they mistake the glowing fireflies of this world as brethren and instinctively begin emulating their actions, thus the similarities that we see between the three families.